The present invention relates to a liquid ejection recording head which ejects different kinds of liquid, such as inks of different colors, onto a recording material such as paper, and more particularly, to a liquid ejection recording head usable with a bi-directional printing apparatus in which the recording is effected with bi-directional scanning of the recording head.
In the field of printing apparatus, particularly ink jet type printing apparatus, there is a demand for high-speed color printing. Various methods adopted for the improvement of recording speed include increasing the length of the recording head, increasing the printing frequency, adopting bi-directional printing, etc. Bi-directional printing is advantageous in the total cost since the necessary energy is dispersed in time for the same throughput as compared with unidirectional printing.
Japanese Laid-Open Patent Application 58-179653 discloses use of forward path nozzles and backward path nozzles as a solution to the problem. In this publication, the operating heads (ejection portions) are switched as between the forward path and the backward path so as to make the orders of ink shots the same irrespective of the scanning direction. The recording head portion comprises a combination of recording heads for ejecting Y (yellow), M (magenta), C (cyan) and Bk (black) inks, respectively. More particularly, as shown in FIG. 3 of that publication, the recording heads are arranged such that Bk, C, M, Y, M, C, and Bk inks are ejected, in this order, both in the forward scanning and the backward scanning. The ink supply to the head portions is made through pipes for the respective heads from the associated ink containers.
However, with the arrangement disclosed in Japanese Laid-Open Patent Application 58-179653, the apparatus is bulky because of the space occupied by the ink supply pipes and the structures for removing bubbles in the pipes.
In view of this, it would be considered, from the standpoint of downsizing the apparatus, that an ink container could be provided for each of the recording heads, with the recording heads and ink containers on a carriage, and bidirectional scanning being used. However, this would result in bulkiness of the carriage, heaviness of the whole apparatus, and an increase in the number of parts, with a resulting cost increase. When use is made of a plurality of ink containers for the same color, the number of ink containers at the time of beginning of use of the apparatus, and therefore the initial cost, are relatively large. Additionally, when it becomes necessary to replace one of the same-color ink containers due to the consumption of the ink, it might not be readily apparent to the user which container should be replaced.
It might also be considered, in an attempt to avoid this problem, that only one ink container is used for the recording heads (ejecting portions) for ejecting ink of a given color. Then, however, the liquid supply passage to the same-color ejection portions from the single container has to be branched. This would result in nonuniform ink supply properties and, therefore, nonuniform ink ejection properties.
More particularly, the printing may be influenced by an increase of flow pressure (resistance) against the ink flow from the ink container to the ejection portion during ink supply (the pressure loss being determined by the length of the supply passage, the supply passage cross-sectional area, the maximum flow speed, the ink viscosity, and so on). If the difference in the pressure losses is large, the ink ejection properties may be different in different ejection portions, and the bubble removing properties may differ significantly. For this reason, it is desirable that pressure loss differences among the ejection portions are small.
Accordingly, it is a principal object of the present invention to provide a liquid ejection recording head and a liquid ejection type recording device in which a recording head and an ink container are carried on a carriage and in which only one ink container is sufficient to cover the same color recording heads, wherein the differences the ink supply properties among in the same-color ejecting portions or the similar color ejecting portions are small.
According to an aspect of the present invention, there is provided a liquid ejection recording head comprising:
a plurality of arrays of ejection outlets for ejecting the same liquid;
common chambers, provided for respective arrays of the ejection outlets, for supplying the liquid to the arrays of the ejection outlets, respectively;
a liquid inlet for receiving the liquid from an outside of said liquid recording head;
a common passage in fluid communication with said liquid inlet;
branched passages branched from said common passage and in fluid communication with said common chambers, respectively,
wherein said branched passages have liquid supply properties which are equivalent to each other.
According to another aspect of the present invention, there is provided a liquid ejection recording head comprising:
a first plurality of arrays of first ejection outlets for ejecting the same first liquid;
a second plurality of arrays of second ejection outlets for ejecting the same second liquid, which is different from the first liquid;
a third plurality of arrays of third ejection outlets for ejecting the same third liquid, which is different from the first liquid and from the second;
first common chambers, provided for respective first arrays of the ejection outlets, for supplying the first liquid to the first arrays of the ejection outlets, respectively;
second common chambers, provided for respective second arrays of the ejection outlets, for supplying the second liquid to the second arrays of the ejection outlets, respectively;
third common chambers, provided for respective third arrays of the ejection outlets, for supplying the third liquid to the third arrays of the ejection outlets, respectively;
a first liquid inlet for receiving the first liquid from outside of said liquid recording head;
a second liquid inlet for receiving the second liquid from outside of said liquid recording head;
a third liquid inlet for receiving the third liquid from outside of said liquid recording head;
a first common passage in fluid communication with said first liquid inlet;
a second common passage in fluid communication with said second liquid inlet;
a third common passage in fluid communication with said second liquid inlet and with said third common chamber;
first branched passages branched from said first common passage and in fluid communication with said first common chambers, respectively, and
second branched passages branched from said second common passage and in fluid communication with said second common chambers, respectively,
wherein said first branched passages have liquid supply properties which are equivalent to each other, and said second branched passages have liquid supply properties which are equivalent to each other.
According to these aspects of the present invention, the possible coloring non-uniformity attributable to the orders of shots of recording droplets particularly in the bi-directional printing operation can be avoided.
According to these aspects of the present invention, only one container is provided for each of different liquids, and therefore, the carriage can be downsized. In addition, the container exchange when the liquid is consumed, is the same as in conventional recording heads which are arranged asymmetrically, and therefore, the replacement is easy for the operator.
It may preferably be that said branched passages are symmetrical with respect to a line perpendicular to a scanning line along which said recording head is moved for scanning.
It may preferably be that said common passage and branched passages constitute a Y-shape. By virtue of this feature, compact arrangement of passages in the liquid jet recording head is accomplished.
In addition, the resistances (pressure loss determined by the length of the supply passage, the supply passage cross-sectional area, the maximum flow speed, the ink viscosity, and so on), for the same kinds of the liquids, against the flow of the liquid from containers to the ejection outlets are substantially the same. As a result, the liquid ejection properties and the bubble removal properties in the supply passages are the same among the ejection outlet arrays for the same kinds of liquids.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.